Objective: To observe the effect of San-Ao Decoction(三拗汤,SAD) on water metabolism of bronchial asthra model mice.Methods: Forty-five female BALB/c mice were randomly divided into control,model and SAD groups by a random number table,15 mice in each group.A composite method with ovalbumin (OVA) sensitization and challenge was developed to establish bronchial asthma model.Mice in the control group were intraperitoneally injected with distilled water without aerosol inhalation challenge.On day 15-22,0.3 mL SAD was administered via gastric route in SAD group,one time per day,while an equivalent volume of normal saline was used for gastric administration in the control and model groups.Changes in airway resistance in the inspiratory phase (RI-R-Area) were detected using an AniRes2005 system,and 5-h urine output was collected by metabolic cages.Histopathological changes in lung and kidney were observed by hematoxylin-eosin staining.mRNA expressions of aquaporin (AQP) 1 and AQP2 in kidney were detected by reverse transcription-polymerase chain reaction,and the protein expressions of AQP1 and AQP2 in kidney were detected by immunohistochemistry.Enzyme-linked immune sorbent assay was used to detect the OVA-specific endothelium-1 (ET-1),antidiuretic hormone (ADH),atrial natriuretic peptide (ANP),prostaglandin E2 (PGE2),and angiotensin Ⅱ (Ang Ⅱ) levels in serum,lung and kidney tissues,respectively.The nitric oxide (NO)contents in serum,lung,and kidney tissues were tested by chemical method,respectively.Results: Compared with the control group,the serum IgE level in model group increased (P＜0.01).Following the pathologic changes in lung tissue,no significant change in kidney tissue was observed among 3 groups.Compared with the control group,the mice in the model group showed elevated airway resistance during inhalation phase,higher mRNA and protein expression levels on AQP1 and AQP2 in kidney tissue and higher ET-1 levels in serum,lung and kidney tissues,ADH and ANP in lung and serum,PGE2 in kidney,Ang Ⅱ in lung and kidney tissues (P＜0.05 or P＜0.01),but decreased in 5-h urinary output as well as NO and PGE2 contents in serum and lung tissues (P＜0.05 or P＜0.01).Compared with the model group,the mice in the SAD group showed a weakened airway resistance in inspiratory phase,lower mRNA and protein expressions of AQP1 and AQP2 in kidney tissues,lower levels of ET-1,ADH,ANP in serum as well as ET-1,ANP,Ang Ⅱ levels in kidney tissues (P＜0.05 or P＜0.01),whereas 5-h urinary output,NO content in kidney,ADH,ANP and PGE2 levels in lung and Ang Ⅱ in serum increased (P＜0.05 or P＜0.01).Conclusion: San-Ao Decoction can regulate the urine volume through regulating AQP1 and AQP2 expression,and the expression of these in the kidneys might be regulated by ET-1,NO and Ang Ⅱ.